API reference

Doors and credentials

Syderial has four doors. Three accept the request formats of the model APIs your clients already call, and the fourth is an MCP server. All four answer from the same record under the same labels.

A door is an endpoint that speaks a protocol your client already knows. Syderial identifies every call through a door, limits it to the caller’s clearance, grounds it in the record and signs a receipt for it.

Door	Method and path	Request format
Chat completions	`POST /v1/chat/completions`	OpenAI chat completions
Messages	`POST /v1/messages`	Anthropic messages
Responses	`POST /v1/responses`	OpenAI responses
Models	`GET /v1/models`	OpenAI models list
MCP door	`POST /mcp`	Model Context Protocol, streamable HTTP

Addresses

Syderial issues door addresses to design partners. These pages write them as https://YOUR-DOOR-ADDRESS for the model doors and https://YOUR-MCP-DOOR-ADDRESS for the MCP door.

Credentials

Syderial issues each credential as a set of request headers. Send them on every call. The Quickstart shows how to load them into the OpenAI and Anthropic SDKs and into curl.

Identity comes from the credential. A request body can’t name its own organization or principal, and the door rejects requests that try.
The door ignores the SDK key field. The OpenAI and Anthropic SDKs require an API key value, so pass any placeholder.
Scopes limit each credential. A credential may call the model doors, capture turns, or both. The door refuses calls outside its scopes.
Your organization’s provider keys. Syderial calls model providers with keys your organization controls.

The MCP door also accepts standard MCP authorization with browser sign-in. See MCP door.

Model aliases

The model field takes an alias configured for your organization. List your aliases to see which ones you can use. The door doesn’t serve a call with an unknown alias.

What Syderial adds to a response

Responses follow each API’s standard format, so standard clients parse them unchanged. Syderial adds the evidence behind the answer and a receipt reference in extra response fields and headers, which standard clients ignore. The design partner reference documents the field names.

Streaming

All three model doors stream server-sent events when the request sets stream to true, in the event format each API defines.

Errors

Errors return an HTTP status and a JSON body with a machine-readable error code.

Status	Meaning
`400`	The request body isn’t valid for the door, or exceeds the limit on messages or tools.
`401`	The credential is missing, incomplete or not recognized.
`403`	The credential lacks the scope for this door.
`429`	Your organization has too many concurrent requests or streams.
`503`	A service the call needs is unavailable. The door doesn’t answer from partial context.